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SUMMARY OF CURRENT RESEARCHES RELATING TO 
cleft which is seen during the development of the lateral Vertebrate 
eye may be explained by supposing that the eye had not at first the 
form of the optic vesicle, but that it was a flattened vesicle, one lateral 
wall of which became the retina, and the other the layer of pigment 
epithelium. It was not till later, when the primitively absent lens 
became developed, that the flattened optic vesicle became the optic cup. 
In this outgrowth of the margins of the flat vesicle we find an explana- 
tion of the cleft. 
Post-Embryonic Development of Ciona and Clavelina.* — Mr. A. 
Willey gives a preliminary account of his observations on the post- 
embryonic development of Ciona intestinalis and Clavelina lepadiform's. 
He finds that the former presents much more primitive features than the 
latter, and he proceeds to compare the conditions in Ciona with those of 
Amphioxus. 
The proboscis cavity of Amphioxus is lined by a flat epithelium, as 
is the rest of the body-cavity ; in Ciona the proboscis cavity contains 
loose endoderm-cells in place of an epithelium, as does the rest of the 
body-cavity ; but the distinction between mesoderm and mesenchym is 
no longer generally recognized as fundamental. 
In instituting any comparison between Ascidians and Amphioxus the 
endostyle should be taken as the starting point, and the fact should be 
remembered that its primary axis is perpendicular to its definite axis in 
both cases. Making allowance for the secondary change of position 
which the mouth has undergone in the larva of Amphioxus , it is found 
that the relative position of the various organs from before backwards 
is precisely the same in Ciona and Amphioxus , viz. (1) proboscis-cavity, 
(2) endostyle, (3) mouth, (4) first pair of gill-slits. 
The author submits the following table of homologies : — 
Ascidians. Amphioxus. 
(a) Proboscis-cavity = Proboscis-cavity and prseoral pit. 
( b ) Endostyle = Endostyle. 
(c) Mouth = Mouth. 
( d ) 1st pair of gill-slits (proper) = 1st pair of gill-slits. 
If these views be correct it is impossible to accept the homology of 
the club-shaped gland of Amphioxus with the intestine of Ascidians, 
which has been suggested by van Beneden and Julin, while they make 
the relations between the two types less strained than they were on the 
views previously entertained. 
Formation of Mantle in Ascidians.f — Prof. A. Kowalevsky finds 
from a study of Phallusia and other forms that the mantle-cells migrate 
from the mesoderm into a superficial mucous layer. There they probably 
serve to increase the tunic-substance, but seem also to act as phagocytes 
both in relation to bacteria and in cases where individuals are moribund. 
The author also describes a number of sections bearing upon doubtful 
points in the morphology of Tunicates. 
A Functional Hermaphrodite Ascidian.J — Prof. W. A. Herdman 
has observed a large Ascidian (probably A. rubicunda ) expelling eggs 
* Proc. Roy. Soc. Lond., li. (1892) pp. 513-20 (3 figs.). 
t Mem. Acad. Imp. Sci. St. Petersb., xxxviii. (1892) pp. 20 (2 pis.). 
X Nature, xlvi. (1892) p. 561. 
